Pressure responsive photoelectric indicating, meansuring, and control device



Oct. 27, 1953 F. c. MELcHloR 2,656,721

' v PRESSURE RESPONSIVE PHOTOELECTRIC INDICATING "MEASURING AND CONTROL DEVICE Filodlug. 26, 1947 3 Sheets-Sheet l w 4 l INVENTOR.

Frederic?? .lelczz'or Oct. 27, 1953 F. c. MELCHLOR 2,656,721

PRESSURE RESPONSIVE PHOTOELECTRIC INDICATING, MEASURING, AND

CONTROL DEVICE med Aug. ze, 1947 s sneets-sneet 2 INVENToR. Frederick CJ/elcz iwf' Oct. 27, 1953 F. c. Mr-:LcHloR 2,656,721

PRESSURE RESPONSIVE PHOTOELECTRIC INDICATING, MEASURING, AND

CONTROL DEVICE Filed Aug. 26, 1947 3 Sheets-Shed 3 Patented Oct. 27, 1953 UNITED (STATES PATIENT OFFICE VDEVICE Frederick CuMelch'ior, New York, IN. Y., assign'or of one-half to `Eiiic B. Melchior, New York,

Appiiesconfaugust 2s, 1947,sernrNo'1i0n44 (ci. nasse) 6 Claims. 1

This invention `relates to instruments or "alpparatus for indicating, and measuring-forces and quantities, and relafted physical factors, and for controlling other instruments and operating devices according to such stimuli. More particularly, it relates to suchap'paratus 'where 'infinite sensitivity and optimum accuracy are required in order to indicateaccurately any infinitesimal change in said stimuli.

The invention also relates to instruments `in which the actuating element may be of the `pressure sensitive variety, such as -altimeters, or o'f the electrical, mechanical Vor thermal variety,

where optimum accuracy 'and infinite sensitivity over the entire operating range are vmost important.

An object of the invention is `to `provide for infinite sensitivity through completely effort less operation of the indicating mechanism o-n the part of the actuating element in addition to elimination of all friction in the mechanism transmitting the motion of the actuating elements.

Another object of the invention is to provide for optimum accuracy by establishing a mathematical point of relative positioning of the trans'- mitting device and the indicating mechanism, for which the entire scale of the instrument may be calibrated.

A further object of the invention is to provide means for generating a differential impulseproportional to departure in either direction from the aforesaid mathematical point of relative positioning between the transmitting device and the indicating or registering mechanism.

A still further object of the invention is to `provide means for amplifying the aforesaid differential for use ih operating a servo-mechanism, either by way of relay for precise indications of values measured, or directly from the amplifying means for control of such values.

It is also an object of this invention, through simple 'and compact design, to incorporate the foregoing desiderata in one unit within the ramifications of bulk and weight commensurate with normal instrument practice in the various elds, thus allowing `any instrument 'to be used at will, as an indicating, recording or controlling instrument.

Additional Aobjects aswell as the exact nature and scope of the invention will be understood from the accompanying drawings illustrating the various details olf the apparatus for 'carrying Vthe invention into effect, and from the following specifications.

Referring *now to 'the drawings:

Fig. "-1 is a longitudinal lcross-sectional View of a typical instrument designed in accordance with the present invention taken on theline l-I of Fig. 2.

Fig. 2 is a longitudinal cross-section taken approximately on theline 2-'-2 of Fig. 1.

Fig. '3 a `front `View of the subject instrument.

Fig. 4 isa to'p view thereof with the face plate and scale removed.

Fig. 15 is a detailed view in 'section ofthe transmitting lever.

Fig. 6 is an enlarged detailed view't'aken on the line 6-46 of Fig. '4 'o'f 'the knob mechanism.

Fig. 7 is a 'diagram of the photo-cell servo circuit.

As may bei'seen "from the drawing, the device chosen to illustrate the invention is in an in strument ofthe pressuresensitivity type in which capsules responding to pressure changes coinprise the actuatingelement. lit is to be noted thatthe exact nature and design of the subject device will `in no way affect the scope and usefulness of my invention which can be used in. ccnnection with many types of measuring, indicating and governing instruments Whereac'curacy, sensitivity vand readability` are of paramount importance. Such devices `may refer to highly diversified applicsations such as thermal instruments for recordings, thermostatic and combustion. control, electrical instruments for measuring and governing over a Wide range and with optimum accuracy a number of factors such as voltage, amperage, magnetic and induction forces, mechanical measurements and recordings for weight balances, precision scales, etc. The illustration as here 'presented is therefore only to be construed as an example of what I consider a simple and logical application vof the basic principle of the invention.

Referring now to Figures 1 and 2, it will be seen that the instrument here illustrated is housed in a conventional case I0 that may well be used for installation in various types of instrument panels. Within the casing I0 is a rigid framework Il which supports the vmechanism `hereinafter de scribed. Affi-fied 4to the framework 1I by anchor plates I2 and I3 are two 'sets of `pressure sensitive capsules l5 and I6 mounted in such a inanner as to substantially oppose each other. Each set may be composed of one or more capsules joined together by any suitable means such as welding or soldering. The saine or other means may be used to anchor them to 'the framework II. The number` of capsules to be used and the size thereof will be determined largely by the space available as well as the range of motion and the power desired for the operation of the transmitting mechanism. These capsules provide the force or motive power by which the structure is actuated. The instrument is set by other means which will be hereinafter described.

The stems of the inner-most capsules are provided with spring strips I'I and IB which are adapted to actuate the lever mechanism hereinafter described. These strips I'I and I8 are preferably made of spring metal. The flexibility or resiliency of these strips is such that the force applied by the capsules through the strips upon the lever mechanism is inadequate and insunlcient to pull or collapse the strips. In other words, the strips are sufficiently rigid to enable them to follow the movements of the lever mechanism hereinafter described.

The free ends of the spring members I1 and I8 are connected to a longitudinally disposed lever I9 suspended by means of a liexure system on brackets 20 and 2|. It will be noted, particularly in Figure 5, that the ilexure system consists of four identical nexures 22, 23, 26 and 25 so arranged that any pivotal movement of the lever I9 will cause rates of deflection which are symmetrical about any axis through the pivotal point of the lever I9. Thus the end of said lever I9, or any point thereon, will always describe a true circle. This is important, as otherwise, the lever may not in all positions conform with the exact point of positioning relative to the indicating device as is required for accuracy of calibration. The strips I1 and I8 connect with the lever I9 at points respectively above and below the theoretical pivotal point of the lever I9. Therefore, when the capsules expand, such as would be the case under decreased pressure, such forward motion on the part of the strips I'I and I8 will cause the lever I9 to pivot in one direction. It will be seen thatthe pressure sensitive mechanism consisting of two sets of capsules, spring strips and transmitting lever suspended by the unique exure system constitutes an exceedingly simple structure.

Referring now to the indicating mechanism and more particularly to Figure 2 and Figure 6, there is mounted at the front end 26 of the casing I6 a knob 32 which is the means whereby the instrument may be set for a given value and an indicating mechanism operated accordingly. Mounted on the side of the casing I9 is a servomotor 21 having a shaft 28 extending through the casing I and carrying a bevel gear 29 which gear 29 is adapted to engage a similar bevel gear 30 mounted on the shaft 33. When the gears 29 and 30 are engaged the knob 32 is inoperative and the device is firmly connected to the servo-motor. When it is desired to operate the instrument manually the gears 29 and 30 may be disengaged by pulling out the knob 32 a small fraction of an inch. This also opens the switch 38 to make the servo-motor inoperative. It will be noted that the shaft 33 has two grooves 34 and 35. As shown in Figure 6 the switch button 3l controlling the switch 38 rides in the groove 3d while a spring loaded ball 39 rides in the groove 35. When the knob is pulled out the entire shaft 33 is moved longitudinally and the switch button 3l rides upwardly out of the groove 34 onto the shaft to open the switch. The ball 39 then rides in the groove 34. The shaft 33 has an extending rod dii which passes through the screw plug 4I and while free to rotate therein is held in place by a nut d2. Teeth 43 are provided on the end of the shaft 33 and are adapted to engage corr..- sponding teeth dfi mounted on the threaded member eil. Since the instrument may be used in a pressurized cabin it may be necessary to vhave it air-tight. The knob is, therefore, made in several portions including a section 45 mounted within the bushing 45 and the outer portion di which is provided with an internal groove adapted to receive the extension d3 of the member 45. When the knob 32 is pulled outwardly it carries with it the rod si), thus moving the shaft 33 longitudinally to engage the teeth i3 and @il and disengage the gears 29 and 30 at the same time operating the switch button 3"?.

Mounted on the shaft 35 splined thereto is a worm 59 which engages two worm gears 5i and 52. The'worm gear 5I is fixedly mounted on a transversely extended shaft 53 equipped with a rigidly mounted pinion 54 which in turn is engaged to an identical pinion 55 rigidly mounted on another transverse shaft 56 which is similar and parallel to the shaft 53. The shafts 53 and 55 are finely threaded with opposite threads` which engage a double nut 5l' bored and threaded through both ends to match the shafts 53 and 56.

From the foregoing it is obvious that when the knob 32 is in the outward position and is turned the worm 59 will cause the worm gears 5I and 52 to rotate in opposite directions. By the same token the rotation of the worm 5I will be directly transmitted by the pinion 54 to the pinion 55 thus causing the shafts 55 and 56 to rotate in opposite directions. As the threads on the shafts as well as in the nut 5l are also opposed, it is evident that the said nut 5'! will be Caused to travel in one direction or another parallel with the longitudinal axis of the shafts 53 and 55.

Referring now to Figure l we find a pivoted member or carriage 6I suspended in bearing bosses 62 and S3 which in turn are nxedly attached to the framework I I. The extreme upper part of the carriage di extends up into and between the two ends of the double nut 5l' resting against a lug or dowel pin 65 in nut 5l on each side thereof, thus preventing the carriage from bypassing the nut 5l. As the carriage 6I is also spring loaded (any conventional spring may be used) against the aforesaid pin 6d, it follows that for any given position of the nut 57, the carriage 5I will maintain a precise corresponding position and will also inevitably follow the nut in its motion over itsentire range of travel.

Fig. 1 and Fig. 2 indicate two photo-electric cells 65 and 55, each with prisms 6'! and 68 rigidly suspended on the carriage 6I. In Fig. 1 there is also shown a light source 69 mounted in an aperture in the carriage 5I in such a manner as to dispose and direct its light substantially into the aforesaid prisms. To this end the light source may be equipped with optical means such as a split lens of suitable shape which will divide the light into two beams, one for each of the prisms, or the light may be diffused so as to substantially cover the area occupied by the prisms. These components constitute an integral part of the indicating mechanism and will always maintain their once determined relative positions. Individually they comprise units known to the art, in current use and should require no further explanation.

Referring now to Fig. 4 we find that the worm 50 engages in addition to the worm gear 5I another worm gear 52 while the latter worm gear is mounted transversely Lon the extended shaft 1I which rotates freely in bearings 12 and 13 `carried by the vframe II. Fixedly mounted on `the shaft 1I is a spool 14. It Awill be seen from the foregoing that when the "knob 32 vis turned by the operator the worm 50 'will cause the `worm gear 52 and hence the shaft 1| .and spool 14 to rotate. It will be evident from the foregoing, therefore, that the worm 50 actuates two mechanisms. rOne is the mechanism by Whi'chthe nut 51 is moved and the other is the mechanism by which the spool 14 is turned. Since the worm V15|) actuates both mechanisms it will be understood that 'the rotary movement of the spool 14 will correspond to the linear movement of the nut 51. The spool 14 fis `provided with a plurality of regularly extended projections, or teeth, 15 which extend along two common `circumferential lines. These projections 15enable the spool `"I4 to act as a sprocket by which the indicating tape 16 having perforations 11 formed therein maybe engaged and advanced in either direction, and when the `sprocket spool 14 is turned, the corresponding movement of the tape 16 will be caused. That is, rotation of the sprocket spool in one direction will `cause movement of the tape in the same direction, and rotation of the sprocket spool in the opposite direction will cause corresponding movement of the tape in the opposite direction.

Reference to Figures 1 `and 2 will show that there are two vspools altogether in the instrument under description. Adjacent sprocketed spool 14 is an idling spool 1B mounted on a shaft 19 in suitable bearings so that the shaft 19 isparallel to the shaft 1I. These two spools are mounted at the front end of the instrument. At the back end of the instrument is a pair of reels 88 and 8 I, these latter reels being rotatably mounted on shafts 82 and 83 whichare `suspended in bosses J 84, 85, 86, and 81 of the frame II. The tape 16 is connected at one end to the reel 88 and at the other end to the reel 8| which extends from reel 88 around spool 14, thence around spool 18 and finally to reel 8|. It will be understood from the foregoing that when the spool 14 is caused to rotate as `above described the tape will be caused'to unwind from one of the reels 80 or 8| and to reel on the other of said reels.

Fig. 2 shows that the reel 80 is provided with a coil spring 88. This spring is attached at one end to the reel 80 and at the other end to a sprocket 89 which turns freely on the shaft 82. Its function is to resist movement of either of these two reels relative to the other and this is accomplished by means of a chain 9|) connecting the sprocket 89 with another sprocket 9| which is rigidly aiiixed to the reel 8|. In consequence it causes the tape 16 to remain at a relatively taut position at all times.

It will be noted in Figures l and 3 that at the front end of the casing I8 is a window 92. This window is fitted with a magnifying lens 93 through which the tape may be viewed. The tape in the embodiment shown in the drawing is provided with calibration designated by the numbers 500, 520, 540 and 560 on the tape in Fig. 3. This calibration may be viewed through the window and through the lens. It will be noted that the tape may carry other calibration designated in a different manner, depending upon the purpose for which the instrument is intended Yto be used.

a givenposition of the lnut `51 and the lcarriage 6I. More specifically, any given reading will correspond to a predetermined position of the members 6I and 51. Thus, it is `obvious that every inch of tape 16 can be `calibrated to 'conform `precisely with the motion Yof the actuating elements thereby avoiding discrepancies inherent in the multi-revolution instruments, where, on the clock principle, the large hand denotes, `for example, a thousand feet of altitude for each revolution. Inasmuch as `no capsules or `bellows are `accurately following `a .straight line `or predetermined graph, it isobvious that such multirevolution instruments are subject to considerable error, whereas, `with the subject arrangement custom calibration will insure `optimum ,accuracy over the'entire operating range.

While the mechanical components `of the transmitting and indicating mechanism have been fully `described it is obvious that there must be provided a mechanism for registering andtranslating into action `the relative rmotions of the transmitting and indicating mechanisms.

In Fig. '7 I show a diagram of a photo-electric circuit embodying known components which `are connected in a novel and practical manner so as to effect the aforementionedobjects of the invention in a simple and superior way. We note the photo-cells 65 and 66, the `amplifier tubes 95 and 96, the relays 91 and 98 and the potentiometer of the variable resistance 99. In addition there is introduced a suitable number of condensers and resisters for the purpose of smoothing or levelling voff excessive peak loads.

In Fig. 5 it will be seen that thelever I9 widens appreciably near its top end I 00,` which'is the portion that passes between the light source and the photo-electric prisms. The width of this lever blade is determined so that it is somewhat less than the combined width of the two light beams entering said prisms. Thus, it may in one position, and in one position only, `relative to the carriage 6I, intercept an equal amount of light from each cell. This, then, is the aforementioned point of equilibrium where the cells are energized to an equal degree and for which the scale may be custom calibrated over its range corresponding with the range of motion of the nut 51 and the carriage 6I. However, as it is practically impossible to maintain any stimuli at a precise constant value for an appreciable period of time, it is evident that even an innitesimal change in such value will cause a slight `movement `of the lever I9 to one side or another and thus a departure from the aforementioned point of equilibrium. This, in turn, will create a differentiai between the two cells, adding more light to one and detracting from the other. Suchdifferentials are amplified by the tubes 95 and 96 causing the relays 91 and 98 to open and close alternately according to the direction oi the motion of the lever I9. These relays are of the ultrasensitive type requiring only minute changes in current to `open and close, and, being balanced against one another to a point where the slightest differential will detract from one and add to the other, they cannot both remain open or closed at the same time but will alternate according to change in stimuli. As the aforesaid point `cf equilibrium is practically mathematical, it follows that the instantaneous action is synonymous with practically infinite sensitivity.

From the foregoing it is also evident that any departure of the lever I9 from the aforementioned point of equilibrium relative to the carriage 6I will cause a differential in the energizing of the cells 65 and B6 and, likewise, that said diiferential may be amplied to any desired degree and, when amplified, may be used to operate one or more servo mechanisms of accepted type, either directly through the pickup from the amplifier tubes 95 and 96 for proportional action, or by way of relays 91 and 98 for decisive or definite action. In some instances it may be desirable to obtain a combination of decisive and proportional action. In such case the amplied differential may be taken from the amplifier tubes 95 and 93 to a photo-electric relay such as is shown in Fig. 7. This photo-electric relay III) consists of a milli-volt meter into which have been installed two photo-electric cells III and II 2, the cathodes of which are exposed to a common light source de by way of the apertures II and H5. In place of the conventional pointer the milli-volt i I il meter has an opaque screen or a disc IIS. Said disc or screen is very light and is perfectly balanced about its axis I I l. In neutral position said disc obscures about onehalf of each of the apertures H4 and II5, thus maintaining equilibrium between the cells I II and H2. However, the moment the differential is generated in the cells 65 and 66 and ampliiied in the tubes 95 and 93, a diiferential in voltage entering the milli-volt meter will cause the disc i I3 to rotate in one direction or another from its neutral position, according to the direction of departure between the lever IS and the carriage S I 'thus admitting more light to one and detracting from the other of the cells II! and H2. As the milli-volt meter is a very sensitive instrument, it is readily seen that in this manner one may obtain any rate and degree of proportional and/or decisive action even for infinitesimal departures from the mathematical point of equilibrium between the lever I9 and the carriage Ii i. In addition, the action lof the milli-volt meter may be speeded up or slowed down by the use of resisters and potentiometer IIB, which, vfurthermore, may be employed to compensate for possible differences in photo-cells which may accrue over long periods of time. rlhis versatility of action is very important as, even for any one application, varying conditions may require a different rate of re-action and governing.

In order to better clarify the operative functions of the invention I shall refer to two broad categories of duties basically: l, as an indicating device; 2, as a controlling device. For use as indicating device the invention must incorporate a suitable servo mechanism for operation of the gear assembly which operates the carriage 6I with its photocells 95 and 66 and light source 99.

Inasmuch as the carriage 6I is synchronized with the tape scale 'iS in a manner hereinabove described it is inevitable that any position which the servo mechanism may cause the carriage 5I to assume will always be identied with the corresponding reading on the tape scale 16. In operation, when the shaft 33 is in the rearward position with the bevel gears 29 yand 30 engaged and the teeth 43 and 44 disengaged, the motor 27 which is geared to the gear I 29 in the conventional -manner is energized by the closing of the switch 3S and operates through the gears 29 and 313 and the worm 50 engaging the gears 5| and 52. This, then, is the condition representing the invention as an indicating device. When due t change in degree or magnitude of stimuli, aifecting the actuating elements I and IB, the lever I9 departs from or bypasses the mathematical point of equilibrium between the photo-cells 65 and 63, a differential is generated in the energizing of the cells, said differential being amplied by the tubes and 96 and causing the relays 98 and 99 to alternately close and open according to the relative position of the lever I9 to that of the carriage 6I, as it changes from one side to the other of the aforesaid mathematical point of equilibrium. As the relays govern the operation of the reversible motor Z'I, it is readily seen that in this manner the motor will operate the carriage 6I so as to always seek equilibrium between the photo-cells and the lever i9, thus also producing an indication of correspon-ding value on the tape scale 7S due to the lever being positioned with the carriage 6I as hereinabove described. In order to change the device into a governing or controlling instrument, it is only necessary to pull out the manual knob 32 until the teeth 43 and 44 engage solidly. It is to be noted that the motion required for such engagements equals the center to center distance between the grooves 34 and 35, and it is, therefore, evident that in the course or such motion the ridge between such grooves will be forced past the ball 39 and the ball Will come to rest in the groove 34, holding the shaft firmly in position. It will also be seen that at the same time the .switch pin o1` button 3l will be depressed to open the switch 38, thus causing the servo motor to be cut out. The instrument can now be set for any given desired value of stimuli by operating the manual knob 32 which in turn operates the carriage EI and the tape scale 16 in the manner previ'ously described. In the first instance, notably that of an indicating device, it was shown how the servomotor was made to operate the carriage BI and thereby also the tape scale so as to seek equilibrium for the photocells with the lever I9. It has been explained how any departure from the aforesaid mathematical point of equilibrium, admitting more light into one photocell than into the other, would generate a diiferential between the energizing of the photocell 65 and that of the similar photocell B9, said differential being ampliiied to operate the relays which in turn govern the operation of the servomotor in a manner so as to always seek to bring the carriage SI back to the point of equilibrium. When the invention is to be used as a governing or controlling device the desired value of stimuli is selected and the indicating mechanism is set for such a value by turning the manual knob 32 until the precise reading is obtained on the tape scale. Such reading must then also conform with a given position of the carriage 3|. Whatever be the value of the stimuli aifecting the actuating capsules I5 and I E it should be noted that the position of the lever I9, whether or not it is intercepting any portion of the light beams to the photocells, will have determined which one of the relays 9i and 98 remain open and which remain closed, depending upon which light beam was the last to be intercepted. In a manner as previously described said relays will now govern another servornotor which likewise will serve to obtain equilibrium between the lever I 9 and the carriage I6. However, in this case, as the carriage is set for a given value the object of the other servomotor will be to adjust the value of the stimuli so as to bring the lever I9 into a position of equilbrium with the photocells E59 and '56 on the carriage SI Such stimuli may, for example, be in the nature of pressure in a laboratory test tank, in which case the relays would operate a motor driving a compressor, and a relief valve as well. However, regardless of the nature of the stimuli, the operation of the photocell circuit in conformance with the relation between the lever I9 and the` carriage 6I remains` the: samev irrespectiveA of whether it makes thea carriage 6I seek equilibriuxnwith the lever I9 as positioned by a given value.A of. stimuli, or whether it makes the lever I9 seek. equilibrium with the carriage 6I by governing such stimuli by way of some outside power source.

It will be understood that in most instances the relays 98 and` 9'I- will be sufficient to govern the control of a` servomotor or other. power source where` decisive or definite action is required. Where proportional action or a` combination of decisive and proportional action is required, the second,v stage relayl III] will be` used in amanner asclearly indicated in Fig. 7.

Referring now to the objects of the invention, itmay be well toreview` some of .its more salient, basic features so as to confirm the manner and measure in which` said objects have been fulfilled.

Asis. clearly shown inFig. 5,.the transmitting lever I9 issuspended. on spring flexures and connected to the actuating elements by similar means, embodying no friction such as is inevitably encountered with pivots or shafts suspended in bearings; likewise, the interception of light beams by the lever I9 involves no friction or effort whatsoever, and it is therefore evident that any reaction orimpulse on the part of the actuating elements is transmitted with infinite sensitivity to the indicating mechanism.

It is also a well known fact. that photo-electric cells are extremely sensitive, say, to one millionth of an inch, and the aforesaid point of equilibrium, established by thelever I9 interceptu ing an equal amount of light from each of the cells (i and 66, may therefore be considered as mathematical. Thus, optimum accuracy depends only upon the actuating elements and is obtainableV insofar as the art of craftsmanship is capable.

Differential in the energizing of the twin-photocells is` an inevitable and immediate consequence of any departure from the aforesaid point of equilibrium, and the amplification of such differential is accomplished by means known to the art. The use of a photo-cell relay, such as shown in Fig. 7, comprising in effect a second stage, further enhances the versatility of the invention and vastly augments the sensitivity and flexii bility of its servo mechanism.

As may be seen from the drawings, there is illustrated an instrument of standard aircraft size, embodying all of the elements of both an indicating and controlling instrument, with4 the exception of the amplifying means which may beconsidered as control accessories. From the description it is also obvious that'theinvention permits of instant change of function from that of an indicating to that of a controlling device bythe mere push or pull on the manual knob 32.

Hereinbefore I have duly described the novel and operative structure of my invention. In ordertolalsounderscore. its usefulness, it may be well to make brief reference. to some ofthe various applications where it will perform its functions in a superior manner. inasmuch as I have chosen to illustrate it in the role of a logical air craft instrument, it may be in order to first stress its utility in this particular field.

(A) As a self-indicating altimeter, with a photo-cell operated servo unit, it will always read true pressure altitude with instant accuracy, ccv ering a range of 80,000 feet or over.

(B)- AsY an` altitude governor, in conventional aircraft operation, it will maintain constant preselected cruising.v altitude by governing the servo of the automatic pilot. This also applies to the circling of airports preparatory` to let-down for landing.

(C) As a landing altimeter, set for a preselected absolute pressure altitude in the final approach for` landing, it will signal the proper height (above the runway) for reducing the rate of descent; or,it will automatically accomplish this through direct servo action without interference on the part of thepilot.

(D) As analtimeter setting instrument, in the airport control towers, with its. photo-cell servo operating arband of selective frequencies aswell as its tape scale, it will automatically and` con tinuously set and zero the altimeters of incoming aircraft having the same type of equipment.

(E) As an altitude control unit, in guided missiles andpilotless aircraft, it will maintain a given pre-selected altitude; or, connected to a` suitable timing unit, it will maintain a series of progressive altitudes according toa prescribed pattern. In the latter case it would become part of an installation for automatic navigation and controlled night paths.

(F) The above altitude control, for use in guided missiles and pilotless aircraft, may be modied to incorporate also a capacitance or sensing element for governing of fuel injection according to altitude and air density.

(G) Referring back to paragraphs C and D, we are looking forward to automatic landings in a reasonably near future. In my opinion, this new instrument will comprise an important component inthe equipment required therefor.

Considering now the marine field, we find the invention almost equally useful. While the potential applications undoubtedly are very numerous, a few of' the' more` important ones will suffice for" the sake of illustration.

As a marine speedometer and speed governor in naval vessels-utilizing the present pilot tube forobtaining dynamic pressure of the water on thesame principle as that which applies to the airspeed indicatorin` the aircraftan instrument designed in accordance with the invention may be calibratedto accurately' indicate the speed through the Water to within one-tenth of a knot. or evenf one-hundredth of a knot if desired. At the same time, by a mere pull on the manual knob, it maybe instantly'set to control the speed of Ithe vessel to Within the aforesaid' margin of anyl desired valueits` photo-cell servo mecha nismv operating the. turbine. governors so as. to obtain for the actuating elements the exact value of stimuli from the' desired speedfor which the indicating' mechanism has been set.

Another application as a pressure sensitive instrumentV would' be that 'ofa depth indicating and control device. Operating in aimanner as hereinbefore described, it would indicate in a submarine `*the exactd'epth below the surface; Likewise, it may instantly be set to control the depth of a submarine or an underwater missile to within a few inches.

As a differential pressure instrument it may be adapted for use as an air/fuel indicator, combination combustion control device, for boiler furnaces and for gas turbines alike. In. this case the actuating elements operate on the pressure dynamic pressure of the" Water:

`drop caused by the flow of air and fuel past a venturi.

There is also the logical possibility of adapting the invention for use as an automatic direction under, with fully automatic and accurate control of the course when desired.

.T n the industrial field, including that of laboratory and test equipment, the applications are so numerous and diverse that it would be futile to here attempt to cover even a small fraction of them. Suice it to say that, in all instances, the principle of operation remains the sameirrespective of whether the instrument indicates and/or controls pressure, temperature, speed, R. P. M., voltage, amperage, weights or other quantities involved. Its usefulness prevails wherever performance requirements call for the optimum in accuracy, sensitivity and readability.

I claim:

l. An indicating device of the type described, H

having a frame, opposing pressure responsive actuating elements mounted in said frame, a pivotal carriage secured to the sides of said frame, said carriage having photo-electric cells mounted on one side thereof and a source of light on the opposite side thereof, a rlever disposed between said cells and light source, said lever being pivotally suspended by fleXure means, means operatively connecting said operating elements to lever, said means comprising flexible spring strips having one end attached to said elements and the opposite end to said lever, one of said strips being attached to said lever above its pivotal point and the other of said strips being attached to said lever below its pivotal point, whereby movement of said lever causes an unbalance in said photo-electric cells, means to indicate said unbalance and means for transmitting electrical energy in proportion to said unbalance.

2. In an instrument of the character described a pair of photo-electric cells, a light source for said cells, a, member pivotally mounted to pass between said light source and said cells to cause an unbalance between said cells, said member being narrower than the combined overall breadth of said cells and covering the area between their centers, to cause a proportional unbalance between said cells and means to transmit said unbalance electrically, said cells having equal portions exposed to light from said light source when said member is in its zero position.

3. An apparatus for pivotally supporting a lever, including four flexure strips and two support members, said support members being positioned on the opposite sides of said lever, said strips being arcuately mounted with one end in each of said strips being secured to said lever, two of said strips being connected to said lever from opposite sides at a position below the pivotal point of said lever.

4. A light sensitive relay including a milli-volt meter, a source of light and two photo-electric cells, said light source being directed at said cells, a rotatable partially opaque disc mounted on the shaft of said milli-volt meter and positioned between said light source and said cells, the remainder of said disc being non-opaque, said disc in its normal position obscuring with its opaque portion a portion of each cell, said cells also having equal portions exposed to light from said light sources through the non-opaque remainder of said disk in its normal position, the illuminated and obscured portions of said cells being arranged so that the rotation of said disk will increase the obscured portion of said cell and decrease the obscured portion of the other cell, means to rotate said disc causing an unbalance in the electrical energy developed by said cells and said unbalance being utilized to selectively operate a servo-motor.

5. An indicating and control device of the type described, including a frame and a pivotal carriage mounted therein, gear means operatively connected to a drum mechanism and two spaced parallel shafts, a nut mounted on said shafts, the upper portion of said carriage positioned between said shafts and operatively connected to said nut, a calibrated tape mounted on said drum mecha nism and means causing said gear means to operate whereby said tape will conform with the position taken by said carriage.

6. An indicating and control device of the type described including a frame and a pivotal carriage mounted therein, gear means operatively connected to a drum mechanism and two spaced parallel shafts, a nut mounted on said shafts, the upper portion of said carriage positioned between said shafts and operatively connected to said nut, actuating means controlling the pivotal movement of said carriage, a calibrated tape mounted on said drum mechanism and means causing said gear means to operate whereby said tape will conform with the position taken by said carriage due to operation of said actuating means.

FREDERICK C. MELCHIOR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,585,210 Roux May 18, 1926 1,690,455 Paulin Nov. 6, 1928 1,761,489 Paulin June 3, 1930 1,822,075 Aronoff Sept. 8, 1931 1,873,579 Haas Aug. 23, 1932 1,914,082 Dennis June 13, 1933 1,929,400 Schulte Oct. 3, 1933 1,930,496 Wilson et al. Oct. 17, 1933 2,067,741 Weckerly Jan. 12, 1937 2,113,436 'Williams Apr. 5, 1938 2,203,284 weckerly July 16, 1940 2,236,255 Young Mar. 25, 1941 2,265,149 Crane et al. Dec. 9, 1941 2,351,081 Swift June 13, 1944 2,376,459 Stevens May 22, 1945 2,410,502 Hurley Nov. 5, 1946 2,503,091 Brooke, Jr., et al. Apr. 4, 1950 2,530,068 McCabe Nov. 14, 1950 OTHER REFERENCES Lange, Photoelements, Reinhold Publishing gforp., New York, copyright 1938, pages 252 and 

